Helminth parasite infracommunities and dietary analysis of the rough-skinned newt, Taricha granulosa from south-eastern Vancouver Island, B.C.

The rough-skinned newt, Taricha granulosa, is a common amphibian in the Pacific Northwest, but very little is known about its helminth parasites. This species typically overwinters on land and returns to breeding ponds in the spring and summer. A primary objective of this study was to determine the nature of parasite infracommunities of the rough-skinned newt. A second was to relate patterns of parasite prevalence and intensity to aspects of rough-skinned newt ecology, including diet. A total of 107 road-killed newts collected in the spring and fall from Doumont Marsh in Lantzville, BC were examined in this study. Necropsies and stomach content analysis were performed on newts in good condition, and snout-vent-length and sex were determined for all newts. Three different parasite species, the trematode, Glypthelmins sp., the acanthocephalan, Neoechinorynchus sp., and the nematode, Cosmocercoides sp. were found in the intestine of newts. The first two were rare, with prevalences of 8 and 4% respectively. Glypthelmins sp. is a new record in this host. Cosmocercoides sp. were found in most newts with a prevalence of 88% and a mean intensity of 3.2 +/- 2.0 worms/host. Prevalence and mean intensity were not influenced by gender, season of collection, or body size. The diets of newts consisted of a wide variety of terrestrial invertebrates, with springtails, snails and mites representing 65% of total prey items observed. This terrestrial diet indicates that newts have limited exposure to parasites transmitted via predator-prey interactions in aquatic habitats. This factor accounts for the low helminth species diversity observed in these newts and the high prevalence and abundance of Cosmocercoides sp., a parasite transmitted by a direct life cycle in terrestrial habitats.